which of the following two codons have double functions?

Options

A. AUG,GUG
B. UAA,UGA
C. UGA,GUG
D. UAA,AUG

Explanation

To determine which two codons have double functions, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Codons**: Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids or signals during protein synthesis.

2. **Identify Functions of Codons**: Codons can have various functions, including coding for amino acids and serving as signals for the start or stop of protein synthesis.

3. **Recognize Initiator Codons**: The initiator codon is crucial for starting the translation process. The most common initiator codon is AUG, which codes for the amino acid methionine.

4. **Look for Dual Function Codons**: We need to find codons that can both code for an amino acid and serve as an initiator.

5. **Examine the Options**:
- **AUG**: This codon codes for methionine and also serves as the start codon for translation.
- **GUG**: This codon can also code for methionine (in some contexts) and can serve as an initiator codon under certain conditions.

6. **Identify Stop Codons**: Other codons such as UAA, UGA, and UAG are known as stop codons. Their sole function is to terminate the translation process, and they do not have dual functions.

7. **Conclusion**: The codons with dual functions are AUG and GUG. Therefore, the correct answer is option number one: AUG and GUG.

### Final Answer:
The two codons that have double functions are **AUG and GUG**.

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